Scanning element for use in television systems



Jan. 24, 1933.

T. A. SMITH 1,895,087

SCANNING ELEMENT FOR USE IN TELEVISION SYSTEMS Filed June 27. 1929 s INVENTOR T.A. SMITH ATTORNEY Patented Jan. 24, 1933 warren STATES PATENT OFFICE- THEODORE A. SMITH, 0F RIDGEWOOD, NEW JERSEY, ASSIGNOR TO RADIO CORPORATION OF AMERICA, .A CORPORATION-OF DELAWARE SCANNING ELEMENT FOR USE IN TELEVISION SYSTEMS Application filed June 27,

The present invention relates to television systems, and, in partlcular, to a scanning element for use in television systems.

Such a scanning element as I have pro vided is adaptable for use in connection with all known and existing types of television transmitters and receivers wherein the television subject or moving picture film, or the like, is adapted to be analyzed and reproduced along a spiral path through the use of disks, drums, mirrors, or the like, in which the disks, drums, or the like, are provided with a number of apertures or lenses arranged about their surface along a spiral path in accordance with the early teachings of Nipkow.

In accordance with the present invention, however, I have sought to develop a method and means by which television subjects, moving picture films, and the like, may be analyzed and reproduced in such a manner that the detrimental effects of flicker occurring in the reproduced subject may be substantially avoided.

As an object of my invention therefore, I have sought to provide a scanning element in which the apertures or lenses are placed thereabouts along a path in which the pitch of the path is equal to the pitch of a corresponding Nipkow spiral, but in which light as projected from or through a television subject or moving picture film, or the like, may be transmitted to a photocell in a broken-up or staggered manner, that is, adjacent parts, bands, or lines of the subject or motion picture film, or the like, will not be sequentially adapted to influence a light sensitive element, or light produced in a light source oooperating with the receiving element will not be adapted to reproduce adjacent or sequential lines on the finished picture.

Other objects and advantages are to provide a scanning element which is relatively simple, easy to construct, convenient to use, and, at the same time, an element which readily adapts itself to all known types of television transmitting and receiving apparatus for the purpose of reducing flicker.

Still further and ancillary objects will hereinafter appear from a consideration of the following specification and claim in con- 1e29. SerialNo. 374,077.

wherein Fig. 1 shows a plane view of a television scanning disk in accordance with my invention; and

Fig. 2 shows diagrammatically and on an enlarged scale, the sequence of various analyzing and reproducing lines as occasioned" by rotation of the scanning disk in a counter clockwise direction, looking at Fig. 1.

Now referring to the drawing, I have shown a disk element 1 having a hub portion 8by which it may be secured to a rotating shaft, or the like, 5 for the purpose of rotation. About the outer surface of the disk, I have arranged a series of apertures 7 which may be holes, or holes in which lenses are positioned. It will be noted that where the various apertures or lenses, a, b, 0, mare considered, that these appear in a stag gered or non-sequential or hit and miss relationship with respect to each other, so

of the picture,and,as shown by Fig. 2, will trace the first line thereof, While the aperture 5 is positioned at a point remote from the aperture a so as to trace line 23, for example, of course assuming that a twenty four line picture is being transmitted and reproduced by a twenty-four aperture disk, as shown. It will also be noted that if the apertures are considered along a path, for example, corresponding to a, f, 2', m, d, t, g, g, o, n, 6, etc., the apertures would appear as the usual N ipkoiv spiral and that, in'such a case, the picture would be scanned along adjacent lines, but that where the aperture a first traversed the picture, the line scanned will be the top line thereof, and the next aperture 6 to scan the picture will produce the twentythird line thereof, as shown by Fig. 2, and the third apertures 0 will produce the twentieth line, while the aperture d will produce the fifth line, and so forth.

lVhile above I have described the location of the various apertures or lenses 7 on the disk 1 as being located by a hit and miss method or in an arbitrary staggeredrelationship with respect to each other, it is also to be recognized that the location may be in accordance with some predetermined mathematical law without departing from j the spirit or scope of the invention.

Therefore, I have produced a scanning element in which the adjacent lines thereofare scanned at widely separated time intervals relatively speaking, during the course 0 transmission. Assume now, i for example,

that the arrangement is applied to the television transmission of motion picture films, then, for example, the motion picture frame corresponding to one position of the subject thereon will be scanned in'such a manner that adjacent partsthereof are reproduced in an irregular order. Thus, there will be substantially no appearance of flicker in the received picture, which would likewise be re- 0 -ceived line for line in the same order as scanned, as outlined above. The disks at the transmitter and receiver should each be positioned correspondingly when the transmission and reception is started and then synchronously operated. The rate of flicker is thuscorrespondingly reduced.

It is particularly noted where the picture is scanned and reproduced along a regular order in which the lines thereof are scanned and reproduced in a sequential manner so that first the top line and then the next line, etc. are reproduced, that a definite band of dark lines appears to move downward with respect to the picture. Such appearance pro- 'duces what is known as flicker and is a distinct function ofthe speed withfwhich the picture is transmitted as regards the number of repetitions a second and is also a function of 'the intensity of the light source,-whereas, 40 if there is no chance for this to occur by reason of the irregular scanning, the flicker frequency substantially disappears. 7 Having now described my invention, what I claim and desire to secure by Letters Pat-'- --ent is the following:

In a television system, a scanning device having a plurality of scanning elements so arranged thereon that each element is spaced a different radial distance from each precedmg and succeeding element.

THEODORE A. SMITH. 

